Rare earth iron-based permanent magnet, method for producing same and use of zirconium alloy

Abstract

This invention discloses a rare-earth iron-based permanent magnet, its preparation method, and the application of zirconium alloy. The preparation method includes the following steps: 1) crushing raw materials comprising rare-earth iron-based alloy coarse powder and at least one zirconium alloy powder using an air jet mill to obtain magnetic powder; based on the weight of the rare-earth iron-based alloy coarse powder, the total amount of zirconium alloy powder is 0.05–0.5 wt%; 2) molding the magnetic powder to obtain a blank, and heat-treating the blank to obtain the rare-earth iron-based permanent magnet; the zirconium alloy powder has the following composition: Zr a Cu b M c Wherein, 25≤a≤70, 20≤b≤70, 1≤c≤20; M is selected from one or more of Hf, Ni, Co, Al, Be, Dy, Tb, Ni, Si, B, Sn, and Ti; where a, b, and c represent the molar or atomic parts of Zr, Cu, and M, respectively. The rare-earth iron-based permanent magnets obtained by the method of this invention possess high magnetic properties.

Description

Technical Field

[0001] This invention relates to a rare earth iron-based permanent magnet, its preparation method, and the use of zirconium alloys. Background Technology

[0002] Neodymium iron boron (Nd-Fe-B) magnets have excellent magnetic properties and have become key functional materials for the development of high-tech industries. The most important aspect of preparing high-performance rare earth iron-based permanent magnet materials is the regulation and optimization of grain boundary phases.

[0003] Currently, NdFeB manufacturers widely employ the addition of rare earth alloys to optimize the grain boundary phase of magnets. CN118782372A discloses a high-coercivity rare earth NdFeB magnet and its preparation method. By adding a certain amount of PrCo5 type alloy micro powder to NdFeB permanent magnet materials, the coercivity of the NdFeB ferromagnet is improved. However, this method requires highly reactive rare earth alloy powders. Furthermore, the particle size of the added auxiliary alloys is critical during magnetic powder mixing; in particular, inappropriate particle size distribution can lead to insufficient mixing with the magnetic powder and agglomeration. In addition, the additional rare earth elements result in a waste of rare earth resources. Low-melting-point rare earth elements can easily cause grain boundary instability, leading to abnormal grain growth, which is detrimental to magnet performance and product quality control.

[0004] In the production process of conventional rare-earth iron-based permanent magnets, elements such as zirconium, copper, aluminum, titanium, and gallium are typically added to improve magnet performance. CN118571636A discloses a rare-earth neodymium iron boron magnet with improved thermal stability. This is achieved through the combined use of high proportions of copper and niobium, which enhances the thermal stability and grain refinement within a normal range. However, achieving a balance between grain size and magnetic properties requires careful adjustment of the copper-niobium ratio; otherwise, problems such as decreased grain boundary phase stability and reduced magnetic properties may occur.

[0005] Zirconium-containing alloys are mainly composed of zirconium, copper, and small amounts of aluminum, titanium, and gallium. They possess outstanding advantages such as high mechanical strength, good chemical stability, and corrosion resistance, and have a wide range of potential applications. However, current production technology for zirconium-containing alloys is demanding, resulting in low material forming rates and yields. Consequently, during normal production, companies inevitably generate a large amount of casting residue and defective products. Summary of the Invention

[0006] In view of this, one object of the present invention is to provide a method for preparing rare-earth iron-based permanent magnets, which can improve the magnetic properties of rare-earth iron-based permanent magnets. Furthermore, this method uses zirconium-containing alloy waste as raw material, reducing production costs and enabling the reuse of zirconium-containing alloy raw materials. Another object of the present invention is to provide a rare-earth iron-based permanent magnet. A further object of the present invention is to provide an application of zirconium-containing alloys. The present invention achieves the above objects using the following technical solutions.

[0007] On the one hand, the present invention provides a method for preparing rare earth iron-based permanent magnets, comprising the following steps:

[0008] 1) The raw materials, including rare earth iron-based alloy coarse powder and at least one zirconium alloy powder, are pulverized by air jet milling to obtain magnetic powder; the total amount of zirconium alloy powder used is 0.05 to 0.5 wt% based on the weight of rare earth iron-based alloy coarse powder.

[0009] 2) The magnetic powder is molded to obtain a blank, and the blank is heat-treated to obtain a rare earth iron-based permanent magnet;

[0010] Rare earth iron-based alloy coarse powder includes:

[0011]

[0012]

[0013] The zirconium alloy powder has the following composition:

[0014] Zr a Cu b M c

[0015] Wherein, 25≤a≤70, 20≤b≤70, 1≤c≤20; M is selected from one or more of Hf, Ni, Co, Al, Be, Dy, Tb, Ni, Si, B, Sn and Ti;

[0016] Where a, b, and c represent the molar or atomic parts of Zr, Cu, and M, respectively.

[0017] According to the preparation method of the present invention, preferably, the zirconium alloy powder is selected from one or more of the following:

[0018] (A) 40≤a≤50, 40≤b≤50, 5≤c≤15, M is Hf, Ni and Co; where the molar ratio of Hf, Ni and Co is (0.5~2):(1~3):(6~8);

[0019] (B) 50≤a≤65, 20≤b≤40, 5≤c≤15, M is Al, Be and Co; where the molar ratio of Al, Be and Co is (7~9):(0.5~3):(0.5~3);

[0020] (C) 25≤a≤40, 50≤b≤70, 1≤c≤5, M is Dy;

[0021] (D) 55≤a≤65, 20≤b≤40, 8≤c≤17, M is Al, Be and Co; where the molar ratio of Al, Be and Co is (7~9):(0.5~3):(0.5~3);

[0022] (E)40≤a≤55,30≤b≤48,5≤c≤15,M is Ni, Si and B;wherein, the molar ratio of Ni, Si and B is (5~7):(2~5):(0.1~1);

[0023] (F) 60≤a≤70, 22≤b≤38, 5≤c≤15, M is Al and Si; where the molar ratio of Al to Si is (7.5~9.5):(0.5~2.5);

[0024] (G)35≤a≤55,30≤b≤45,10≤c≤20,M is Al, Ti and Co; wherein the molar ratio of Al, Ti and Co is (1~4):(4.5~7.5):(0.1~1).

[0025] According to the preparation method of the present invention, preferably, the zirconium alloy powder has a C content of less than or equal to 1000 ppm, an O content of less than or equal to 1500 ppm, and a N content of less than or equal to 1000 ppm.

[0026] According to the preparation method of the present invention, preferably, the raw materials further contain one or more of antioxidants and lubricants;

[0027] The antioxidant is selected from one or more of the following: triethanolamine, methyl octanoate, methyl lauryl oleate, isooctyl oleate, methyl palmitate, methyl oleate, triethanolamine oleate, and tributyl borate.

[0028] Based on the mass of rare earth iron-based alloy coarse powder, the lubricant dosage is 0.2–1.8 wt‰;

[0029] The lubricant is selected from amide compounds containing 10 to 40 carbon atoms.

[0030] According to the preparation method of the present invention, preferably, the zirconium alloy powder is amorphous, and the source of the zirconium alloy powder includes slag, casting residue, and defective products.

[0031] According to the preparation method of the present invention, preferably, the heat treatment in step 2) includes the following steps: sintering at a temperature of 1050–1125°C for 2–6 hours to obtain a sintered body; subjecting the sintered body to a first-stage aging treatment at 880–950°C for 0.5–5 hours; and then subjecting it to a second-stage aging treatment at 400–630°C for 2–5 hours to obtain the rare-earth iron-based permanent magnet.

[0032] On the other hand, the present invention provides a rare earth iron-based permanent magnet, which is prepared by the above-described preparation method.

[0033] According to the rare-earth iron-based permanent magnet of the present invention, preferably, the rare-earth iron-based permanent magnet contains a zirconium-containing compound, which is distributed in at least one region as shown below in the form of laths and / or regular particles:

[0034] (I) Grain boundary region;

[0035] (II)Re2Fe 14 B main phase grain edges.

[0036] In another aspect, the present invention provides the use of zirconium alloy in improving the magnetic properties of rare earth iron-based permanent magnets, characterized in that the zirconium alloy has the following composition:

[0037] Zr a Cu b M c

[0038] Wherein, 25≤a≤70, 20≤b≤70, 1≤c≤20; M is selected from one or more of Hf, Ni, Co, Al, Be, Dy, Tb, Ni, Si, B, Sn and Ti;

[0039] Where a, b, and c represent the molar or atomic parts of Zr, Cu, and M, respectively;

[0040] The rare earth iron-based permanent magnet includes:

[0041]

[0042] According to the use of the invention, preferably, the magnetic properties are selected from one or more of coercivity, remanence, and maximum energy product.

[0043] This invention utilizes zirconium-containing alloy recycled materials as alloy additives in the preparation of high-performance rare-earth iron-based permanent magnets, reducing the huge consumption and heavy dependence on rare-earth resources of the current mainstream grain boundary rare-earth auxiliary alloying method, and solving the problem of high-value recycling of zirconium-containing alloy recycled materials. In addition, the method of this invention optimizes the microstructure and phase composition of the neodymium-rich phase of the magnet by using high-melting-point compounds formed by the in-situ reaction of zirconium and copper elements in the zirconium-containing alloy, eliminating the adverse effects of harmful impurity elements on performance, and achieving a significant improvement in magnet performance and effective control of manufacturing costs. Attached Figure Description

[0044] Figure 1 This is a SEM image of the rare earth iron-based permanent magnet obtained in Example 1 of the present invention, wherein zirconium exists in lath form in the grain boundary phase.

[0045] Figure 2 This is a SEM image of the rare earth iron-based permanent magnet obtained in Example 2 of the present invention, wherein zirconium exists in lath form in the grain boundary phase.

[0046] Figure 3 This is a SEM image of the rare earth iron-based permanent magnet obtained in Example 3 of the present invention, wherein zirconium exists in granular form in the grain boundary phase.

[0047] Figure 4 This is a SEM image of the rare earth iron-based permanent magnet obtained in Example 4 of the present invention, wherein zirconium exists in granular form in the grain boundary phase.

[0048] Figure 5 This is a SEM image of the rare earth iron-based permanent magnet obtained in Example 5 of the present invention, wherein zirconium exists in granular form in the grain boundary phase. Detailed Implementation

[0049] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0050] The "remanence" mentioned in this invention refers to the ability of a magnet to maintain a certain magnetization intensity in the original direction of the external magnetic field after the magnet has been magnetized to saturation and the external magnetic field has been removed. It is usually denoted as B. r The unit is Tesla (T) or Gauss (G).

[0051] The "coercivity" mentioned in this invention refers to "intrinsic coercivity," which is the strength of the reverse magnetic field applied when the vector sum of the microscopic magnetic dipole moments inside the magnet drops to zero, usually denoted as H. cj The unit is ozt (Oe) or ampere per meter (A / m).

[0052] The "vacuum degree" mentioned in this invention refers to the absolute vacuum degree; the smaller the value, the higher the vacuum degree.

[0053] <Preparation Methods of Rare Earth Iron-Based Permanent Magnets>

[0054] This invention uses zirconium-containing alloys to prepare rare-earth iron-based permanent magnet materials. After crushing, the alloys are uniformly mixed with magnetic powder, and the high-temperature sintering process is used to preferentially liquefy them and obtain high-quality grain boundary phases. This reduces the consumption of rare-earth elements while obtaining high-performance rare-earth iron-based permanent magnet materials.

[0055] The preparation method of the present invention includes the following steps: 1) an air jet milling step; and 2) a molding and sintering step. Each step is described in detail below.

[0056] Steps of air jet mill

[0057] The present invention uses air jet milling of raw materials comprising rare earth iron-based alloy coarse powder and at least one zirconium alloy powder to obtain magnetic powder.

[0058] Particle size D of rare earth iron-based alloy coarse powder 50 It can be 100-200μm; preferably 120-160μm; more preferably 130-140μm.

[0059] The raw materials can be vacuum smelted and spun to obtain rare earth iron-based alloy strips; the rare earth iron-based alloy strips can be hydrogen-crushed to obtain rare earth iron-based alloy coarse powder.

[0060] Rare earth iron-based alloy coarse powder may contain Pr, Nd, Cu, Co, Al, Ga, Zr, B, and Fe. Preferably, the rare earth iron-based alloy powder is composed of the above-mentioned elements.

[0061] The total content of Pr and Nd can be 20 to 38 parts by weight; preferably 25 to 35 parts by weight; more preferably 29 to 32 parts by weight. The mass ratio of Pr to Nd can be 25:(60 to 85); preferably 25:(70 to 80); more preferably 25:(75 to 78).

[0062] The Cu content can be 0.05 to 0.5 parts by weight; preferably 0.1 to 0.3 parts by weight. In some embodiments, the Cu content is 0.15 to 0.18 parts by weight.

[0063] The Co content can be 0.1 to 1 part by weight; preferably 0.3 to 0.8 parts by weight. In some embodiments, the Co content is 0.5 to 0.6 parts by weight.

[0064] The Al content can be 0.1 to 1 part by weight; preferably 0.3 to 0.8 parts by weight; more preferably 0.4 to 0.5 parts by weight.

[0065] The Ga content can be 0.05 to 0.5 parts by weight; preferably 0.1 to 0.3 parts by weight. In some embodiments, the Ga content is 0.2 to 0.25 parts by weight.

[0066] The Zr content can be 0.05 to 0.5 parts by weight; preferably 0.1 to 0.3 parts by weight. In some embodiments, the Zr content is 0.15 to 0.2 parts by weight.

[0067] The content of B can be 0.7 to 1 part by weight; preferably 0.8 to 0.95 parts by weight. In some embodiments, the content of B is 0.9 to 0.92 parts by weight.

[0068] The Fe content can be 60-75 parts by weight; preferably 65-70 parts by weight; more preferably 67-68.5 parts by weight.

[0069] The combination of the rare earth iron-based alloy coarse powder composed of the above elements with the zirconium alloy powder of the present invention further helps to improve the magnetic properties of rare earth iron-based permanent magnets, so that the magnets have higher remanence, coercivity and maximum energy product.

[0070] The zirconium alloy powder of this invention can be obtained by processing zirconium-containing alloy waste. The zirconium-containing alloy waste can be amorphous or crystalline; preferably amorphous. The zirconium-containing alloy waste mainly comes from casting residues, substandard castings, slag, etc., formed during the preparation of amorphous alloys but which cannot be directly recycled.

[0071] Zirconium alloy waste can be surface-treated to remove impurities and then crushed to obtain zirconium alloy powder.

[0072] Surface impurity removal can be performed using methods commonly used in the art, such as sandblasting or ultrasonic cleaning. The sandblasting pressure can be 0.3–0.9 MPa; preferably 0.4–0.7 MPa. The sandblasting medium can be brown corundum. Ultrasonic cleaning can be performed in small molecule alcohols containing 1–6 carbon atoms, such as methanol, ethanol, propanol, and isopropanol.

[0073] The crushing process can be carried out first by mechanical crushing, and then by disc milling.

[0074] Particle size D of zirconium alloy powder 50 It can be 3 to 15 μm; preferably 5 to 10 μm; more preferably 6 to 8 μm.

[0075] Zirconium alloy powder can have the following composition:

[0076] Zr a Cu b M c

[0077] 'a' represents the molar or atomic number of Zr. 25 ≤ a ≤ 70; preferably, 30 ≤ a ≤ 65.

[0078] b represents the molar or atomic number of Cu. 20 ≤ b ≤ 70; preferably, 30 ≤ b ≤ 65.

[0079] c represents the molar or atomic number of M. 1 ≤ c ≤ 20; preferably, 5 ≤ c ≤ 10.

[0080] M is selected from one or more of Hf, Ni, Co, Al, Be, Dy, Tb, Ni, Si, Sn, B, and Ti. Preferably, M is selected from the elemental composition shown in one of the following: (A) M is Hf, Ni, and Co; (B) M is Al, Be, and Co; (C) M is Dy; (D) M is Ni, Si, and B; (E) M is Al and Si; (F) M is Al, Ti, and Co.

[0081] In some embodiments, the zirconium alloy powder is selected from one or more of the following:

[0082] (A) 40≤a≤50, 40≤b≤50, 5≤c≤15, M is Hf, Ni and Co; wherein the molar ratio of Hf, Ni and Co is (0.5~2):(1~3):(6~8). Preferably, 44≤a≤47, 46≤b≤48, 10≤c≤12. Preferably, the molar ratio of Hf, Ni and Co is (1~1.5):(2~2.5):(7~7.5).

[0083] (B) 50≤a≤65, 20≤b≤40, 5≤c≤15, M is Al, Be, and Co; wherein the molar ratio of Al, Be, and Co is (7~9):(0.5~3):(0.5~3). Preferably, 58≤a≤60, 30≤b≤35, 10≤c≤12. Preferably, the molar ratio of Al, Be, and Co is (8~8.5):(1~2):(1~2).

[0084] (C) 25≤a≤40, 50≤b≤70, 1≤c≤5, M is Dy. Preferably, 30≤a≤35, 65≤b≤68, 2≤c≤4.

[0085] (D) 55≤a≤65, 20≤b≤40, 8≤c≤17, M is Al, Be, and Co; wherein the molar ratio of Al, Be, and Co is (7~9):(0.5~3):(0.5~3). Preferably, 58≤a≤60, 30≤b≤35, 10≤c≤12. Preferably, the molar ratio of Al, Be, and Co is (8~8.5):(1~2):(1~2).

[0086] (E) 40≤a≤55, 30≤b≤48, 5≤c≤15, M is Ni, Si and B; wherein the molar ratio of Ni, Si and B is (5~7):(2~5):(0.1~1). Preferably, 50≤a≤55, 35≤b≤40, 10≤c≤12. Preferably, the molar ratio of Ni, Si and B is (6~6.5):(3.5~4):(0.5~0.8).

[0087] (F) 60≤a≤70, 22≤b≤38, 5≤c≤15, M is Al and Si; wherein the molar ratio of Al to Si is (7.5~9.5):(0.5~2.5). Preferably, 65≤a≤68, 25≤b≤27, 5≤c≤10. Preferably, the molar ratio of Al to Si is (8.6~9):(1~1.4).

[0088] (G) 35≤a≤55, 30≤b≤45, 10≤c≤20, M is Al, Ti and Co; wherein the molar ratio of Al, Ti and Co is (1~4):(4.5~7.5):(0.1~1). Preferably, 40≤a≤44, 40≤b≤42, 15≤c≤16. Preferably, the molar ratio of Al, Ti and Co is (2~3):(6.5~7):(0.5~0.8).

[0089] According to one embodiment of the present invention, the zirconium alloy powder is a combination of zirconium alloy powder as shown in (D), zirconium alloy powder as shown in (E), and zirconium alloy powder as shown in (F). The mass ratio of the zirconium alloy powder as shown in (D), the zirconium alloy powder as shown in (E), and the zirconium alloy powder as shown in (F) is (6-10):(10-15):(70-90); preferably (7-9):(12-13):(75-80).

[0090] The carbon content in the zirconium alloy powder is less than or equal to 1000 ppm; preferably, it is less than or equal to 800 ppm. In some embodiments, the carbon content is 300–650 ppm.

[0091] The oxygen content in the zirconium alloy powder is less than or equal to 1500 ppm; preferably, it is less than or equal to 1300 ppm. In some embodiments, the oxygen content in the zirconium alloy powder is 600–1200 ppm.

[0092] The nitrogen content in the zirconium alloy powder is less than or equal to 1000 ppm; preferably, it is less than or equal to 700 ppm. In some embodiments, the nitrogen content is 300–650 ppm.

[0093] The aforementioned zirconium alloy powder helps to improve the magnetic properties of rare earth iron-based permanent magnets.

[0094] The total amount of zirconium alloy powder used is 0.05 to 0.5 wt% based on the weight of the rare earth iron-based alloy powder; preferably 0.1 to 0.4 wt%. In some embodiments, the total amount of zirconium alloy powder used is 0.2 to 0.3 wt% based on the weight of the rare earth iron-based alloy powder.

[0095] This invention discovers that by controlling the total amount of zirconium alloy powder within the above-mentioned range, the metallic elements such as zirconium and copper can be highly overlapped with the main elements of the rare earth iron-based alloy coarse powder to be mixed, and the adverse effects of harmful impurity elements on the performance of rare earth iron-based magnet materials can be eliminated, thereby improving the coercivity and mechanical properties of the prepared rare earth iron-based magnet.

[0096] In some embodiments, the original material also contains one or more of antioxidants and lubricants.

[0097] The antioxidant can be a carboxylic acid derivative. Specifically, the antioxidant is selected from one or more of methyl octanoate, triethanolamine, methyl laurate, isooctyl oleate, methyl oleate, and triethanolamine oleate. Based on the mass of the rare earth iron-based alloy powder, the amount of antioxidant can be 0.1–3 wt‰; preferably 0.5–2 wt‰; more preferably 0.9–1.5 wt‰.

[0098] The lubricant can be selected from amide compounds containing 10 to 40 carbon atoms. Specifically, it can be selected from at least one of oleamide, erucamide, and ethylene bis-stearamide. Based on the mass of the rare earth iron-based alloy powder, the amount of lubricant can be 0.2 to 1.8 wt‰; preferably 0.3 to 1.5 wt‰; more preferably 0.5 to 0.9 wt‰.

[0099] Air jet mills can form raw materials with a particle size D 50 The powder has a particle size of 1–10 μm; preferably 2–8 μm; more preferably 3–4 μm.

[0100] This invention discovers that when zirconium alloy powder and rare earth iron-based alloy coarse powder are mixed and then crushed to the particle size range mentioned above by an air jet mill, the two can be fully mixed and are not prone to agglomeration, which is beneficial to the control and optimization of the grain boundary phase of the sintered magnet material.

[0101] The steps of forming and sintering

[0102] The present invention obtains a blank by forming magnetic powder, and then heat-treats the blank to obtain a rare earth iron-based permanent magnet.

[0103] Magnetic powder can be oriented and pressed in a magnetic field to form a shape. In some embodiments, the blank obtained by orientation pressing is directly heat-treated. In other embodiments, the blank obtained by orientation pressing is isostatically pressed and then heat-treated.

[0104] The density of the green body obtained by orientation pressing can be 3-6 g / cm³. 3 The preferred concentration is 3.5–5 g / cm³. 3 More preferably, 4–4.5 g / cm³ 3 .

[0105] The heat treatment may include the following steps: sintering at 1050–1125℃ for 2–6 hours to obtain a sintered body; subjecting the sintered body to a first-stage aging treatment at 880–950℃ for 0.5–5 hours; and then subjecting it to a second-stage aging treatment at 400–630℃ for 2–5 hours. The heat treatment can be performed in a vacuum heat treatment furnace. The heat treatment can be performed under a pressure less than 10 Pa.

[0106] The sintering temperature can be 1050–1125℃; preferably 1065–1110℃; more preferably 1080–1095℃.

[0107] The sintering time can be 2 to 6 hours; preferably 2.5 to 5.5 hours; more preferably 3 to 5 hours.

[0108] After sintering, the resulting product can be cooled to 20-35°C by forced air cooling to obtain a sintered body.

[0109] The primary aging treatment temperature can be 880–950℃; preferably 890–940℃; more preferably 900–930℃.

[0110] The first-level efficiency processing time can be 0.5 to 5 hours; preferably 1 to 4 hours; more preferably 1.5 to 3 hours.

[0111] The secondary aging treatment temperature can be 400–630℃; preferably 450–600℃; more preferably 500–570℃.

[0112] The processing time for the second-level time-sensitive treatment can be 2 to 5 hours; preferably 2.5 to 4.5 hours; and preferably 3 to 4 hours.

[0113] The aged product can be rapidly cooled to 20–35°C to obtain rare-earth iron-based permanent magnets. Nitrogen gas can be used for cooling.

[0114] By employing such heat treatment conditions, the depth of rare earth element diffusion into the magnet can be controlled, thereby improving the magnet's coercivity while avoiding a decrease in remanence. This invention reveals that zirconium alloy powder, when subjected to the aforementioned high-temperature sintering process, can preferentially liquefy to form zirconium-containing high-melting-point compounds. These compounds are primarily composed of borides and carbides, followed by small amounts of nitrides and oxides, and are distributed in lath-like and / or regular particle forms in the grain boundary regions, or in the Re2Fe matrix. 14 B. Main phase grain edges. Zirconium-containing high-melting-point compounds can suppress the growth of main phase grains during high-temperature sintering, obtain high-quality grain boundary phases, and obtain high-performance rare-earth iron-based permanent magnet materials while reducing rare-earth element consumption.

[0115] Rare earth iron-based permanent magnets

[0116] The rare-earth iron-based permanent magnet of the present invention is prepared by the above method. The rare-earth iron-based permanent magnet of the present invention contains zirconium-containing compounds. These zirconium-containing compounds are distributed in the rare-earth iron-based permanent magnet in the form of laths and / or regular particles. The regular particles are, for example, cubic-like structures. Specifically, the zirconium-containing compounds are distributed in the grain boundary regions and / or Re2Fe. 14 B main phase grain edges.

[0117] Applications of Zirconium Alloys

[0118] This invention discovers that the addition of appropriate zirconium alloys to rare-earth iron-based permanent magnets can improve their magnetic properties. Therefore, this invention provides an application of zirconium alloys in improving the magnetic properties of rare-earth iron-based permanent magnets. Compared to rare-earth iron-based permanent magnets without added zirconium alloy powder, the addition of zirconium alloy powder increases the coercivity by 2% to 15% and the maximum energy product by 1.5% to 3%.

[0119] Zirconium alloys have the following composition:

[0120] Zr a Cu b M c

[0121] Wherein, 25≤a≤70, 20≤b≤70, 1≤c≤20; M is selected from one or more of Hf, Ni, Co, Al, Be, Dy, Tb, Ni, Si, Sn, B and Ti;

[0122] Where a, b, and c represent the molar or atomic parts of Zr, Cu, and M, respectively.

[0123] Based on the mass of the rare earth iron-based magnet, the amount of zirconium alloy can be 0.05–0.5 wt%; preferably 0.1–0.4 wt%. In some embodiments, the total amount of zirconium alloy powder is 0.2–0.3 wt% based on the weight of the rare earth iron-based alloy coarse powder.

[0124] Zirconium alloys can be used in the form of zirconium alloy powder. Details of zirconium alloys have been described above and will not be repeated here.

[0125] Rare earth iron-based permanent magnets may contain Pr, Nd, Cu, Co, Al, Ga, Zr, B, and Fe. Preferably, the rare earth iron-based alloy powder is composed of the above elements.

[0126] The total content of Pr and Nd can be 20 to 38 parts by weight; preferably 25 to 35 parts by weight; more preferably 29 to 32 parts by weight. The mass ratio of Pr to Nd can be 25:(60 to 85); preferably 25:(70 to 80); more preferably 25:(75 to 78).

[0127] The Cu content can be 0.05 to 0.5 parts by weight; preferably 0.1 to 0.3 parts by weight. In some embodiments, the Cu content is 0.15 to 0.18 parts by weight.

[0128] The Co content can be 0.1 to 1 part by weight; preferably 0.3 to 0.8 parts by weight. In some embodiments, the Co content is 0.5 to 0.6 parts by weight.

[0129] The Al content can be 0.1 to 1 part by weight; preferably 0.3 to 0.8 parts by weight; more preferably 0.4 to 0.5 parts by weight.

[0130] The Ga content can be 0.05 to 0.5 parts by weight; preferably 0.1 to 0.3 parts by weight. In some embodiments, the Ga content is 0.2 to 0.25 parts by weight.

[0131] The Zr content can be 0.05 to 0.5 parts by weight; preferably 0.1 to 0.3 parts by weight. In some embodiments, the Zr content is 0.15 to 0.2 parts by weight.

[0132] The content of B can be 0.7 to 1 part by weight; preferably 0.8 to 0.95 parts by weight. In some embodiments, the content of B is 0.9 to 0.92 parts by weight.

[0133] The Fe content can be 60-75 parts by weight; preferably 65-70 parts by weight; more preferably 67-68.5 parts by weight.

[0134] Specifically, the process includes the following steps: 1) pulverizing raw materials, including rare earth iron-based alloy coarse powder and at least one zirconium alloy powder, through an air jet mill to obtain magnetic powder;

[0135] 2) The magnetic powder is molded to obtain a blank, and the blank is heat-treated to obtain the rare earth iron-based permanent magnet.

[0136] The specific steps are as described above and will not be repeated here.

[0137] The test method is described below:

[0138] SEM: Tested using a Zeiss Sigma 500 field emission scanning electron microscope.

[0139] Particle size D 50 The test was conducted using a laser particle size analyzer.

[0140] Magnetic properties: Sintered NdFeB magnets were cut into cylinders with a diameter of 10 mm and a height of 8 mm for magnetic property testing. The testing instrument was NIM-10000HC.

[0141] The raw materials are described below:

[0142] The antioxidant is isooctyl oleate.

[0143] The lubricant is erucamide.

[0144] Example 1

[0145] The raw materials are vacuum smelted to obtain rare earth iron-based alloy strips; the rare earth iron-based alloy strips are then hydrogen-crushed to obtain rare earth iron-based alloy coarse powder. The particle size D of the rare earth iron-based alloy coarse powder is... 50 The particle size is 128 μm. The composition of the rare earth iron-based alloy coarse powder is: PrNd 29.8 wt%, Cu 0.18 wt%, Co 0.3 wt%, Al 0.5 wt%, Ga 0.1 wt%, Zr 0.16 wt%, B 0.90 wt%, Fe balance. The mass ratio of Pr to Nd is 25:75.

[0146] Sandblasting removes impurities such as slag and oxides from the surface of zirconium-containing amorphous alloy casting residue, yielding treated zirconium-containing waste. The sandblasting pressure is 0.6 MPa, and the sandblasting medium is 50-mesh brown corundum. The treated zirconium-containing waste is then mechanically crushed to a particle size of less than 1 mm, and then milled with petroleum ether to obtain a particle size D. 50 The zirconium alloy powder has a thickness of 8.6 μm. The chemical composition of the zirconium alloy powder is Zr. 44 Cu 46 M 10 The zirconium alloy powder contains Hf, Ni, and Co elements in a molar ratio of 10:20:70. The powder contains 624 ppm C, 942 ppm O, and 445 ppm N.

[0147] Zirconium alloy powder was added to rare earth iron-based alloy coarse powder and then fed into an air jet mill. Antioxidants and lubricants were then added, and the mixture was crushed to obtain a particle size D. 50 The magnetic powder has a particle size of 4 μm. Based on the mass of rare earth iron-based alloy coarse powder, the amount of zirconium alloy powder is 0.35 wt%, the amount of antioxidant is 0.3 wt‰, and the amount of lubricant is 0.85 wt‰.

[0148] The magnetic powder was oriented and pressed in a magnetic field to obtain a density of 4.22 g / cm³. 3 The blank.

[0149] The blank was sintered at 1090℃ for 6 hours, and then cooled to 25℃ by forced air to obtain a sintered body. The sintered body was subjected to a first-stage aging treatment at 940℃ for 0.5 hours, followed by a second-stage aging treatment at 550℃ for 4 hours. After the second-stage aging treatment, nitrogen gas at 25℃ was introduced and cooled to 25℃ to obtain a rare earth iron-based permanent magnet.

[0150] Comparative Example 1

[0151] Except for the absence of zirconium alloy powder, it is the same as in Example 1.

[0152] The performance test results of the rare earth iron-based permanent magnets obtained in Example 1 and Comparative Example 1 are shown in Table 1.

[0153] Table 1 Performance test results of rare earth iron-based permanent magnets

[0154] serial number Remanence / kGs Coercivity / kOe Maximum magnetic energy product / MGOe Example 1 14.55 14.48 52.40 Comparative Example 1 14.43 12.67 51.02

[0155] Example 2

[0156] The raw materials are vacuum smelted to obtain rare earth iron-based alloy strips; the rare earth iron-based alloy strips are then hydrogen-crushed to obtain rare earth iron-based alloy coarse powder. The particle size D of the rare earth iron-based alloy coarse powder is... 50 The particle size is 156 μm. The composition of the rare earth iron-based alloy coarse powder is: PrNd 30.4 wt%, Cu 0.10 wt%, Co 0.4 wt%, Al 0.5 wt%, Ga 0.2 wt%, Zr 0.2 wt%, B 0.92 wt%, Fe balance. The mass ratio of Pr to Nd is 25:75.

[0157] A zirconium-containing amorphous ribbon with a width of 3 mm and a thickness of 50 μm was ultrasonically cleaned in anhydrous ethanol for 30 minutes, then mechanically crushed to a particle size of less than 1 mm; subsequently, it was added to petroleum ether and disc-milled to obtain a particle size D. 50 The zirconium alloy powder has a particle size of 5.5 μm. The chemical composition of the zirconium alloy powder is Zr. 58 Cu 30 M 12 The zirconium alloy powder contains Al, Be, and Co elements in a molar ratio of 80:10:10. The powder contains 424 ppm of carbon, 1242 ppm of oxygen, and 462 ppm of nitrogen.

[0158] Zirconium alloy powder was added to rare earth iron-based alloy coarse powder and then fed into an air jet mill. An antioxidant was then added, and the mixture was crushed to obtain a particle size D. 50 The magnetic powder has a particle size of 3.5 μm. Based on the mass of rare earth iron-based alloy coarse powder, the amount of zirconium alloy powder used is 0.28 wt%, and the amount of antioxidant used is 0.9 wt‰.

[0159] The magnetic powder was oriented and pressed in a magnetic field to obtain a density of 4.1 g / cm³. 3 The pre-pressed billet is then subjected to isostatic pressing to obtain the billet.

[0160] The blank was sintered at 1080℃ for 4.5 hours, and then cooled to 25℃ by forced air to obtain a sintered body. The sintered body was subjected to a first-stage aging treatment at 945℃ for 1 hour, followed by a second-stage aging treatment at 520℃ for 3 hours. After the second-stage aging treatment, nitrogen gas at 25℃ was introduced and cooled to 25℃ to obtain a rare earth iron-based permanent magnet.

[0161] Comparative Example 2

[0162] Except for the absence of zirconium alloy powder, it is the same as in Example 2.

[0163] The performance test results of the rare earth iron-based permanent magnets obtained in Example 2 and Comparative Example 2 are shown in Table 2.

[0164] Table 2 Performance test results of rare earth iron-based permanent magnets

[0165] serial number Remanence / kGs Coercivity / kOe Maximum magnetic energy product / MGOe Example 2 14.32 15.21 50.75 Comparative Example 2 14.16 14.67 49.63

[0166] Example 3

[0167] The raw materials are vacuum smelted to obtain rare earth iron-based alloy strips; the rare earth iron-based alloy strips are then hydrogen-crushed to obtain rare earth iron-based alloy coarse powder. The particle size D of the rare earth iron-based alloy coarse powder is... 50 The particle size is 134 μm. The composition of the rare earth iron-based alloy coarse powder is: PrNd 30.1 wt%, Cu 0.15 wt%, Co 0.35 wt%, Al 0.4 wt%, Ga 0.15 wt%, Zr 0.15 wt%, B 0.95 wt%, Fe balance. The mass ratio of Pr to Nd is 25:75.

[0168] Defective zirconium-containing amorphous alloy castings were sandblasted to remove surface slag, oxides, and other impurities, yielding treated zirconium-containing waste. The sandblasting pressure was 0.6 MPa, and the sandblasting medium was 50-mesh brown corundum. The treated zirconium-containing waste was mechanically crushed to a particle size of less than 1 mm, then added to a petroleum ether disc mill to obtain a particle size D. 50 The zirconium alloy powder has a thickness of 5.6 μm. The chemical composition of the zirconium alloy powder is Zr. 30 Cu 68 M2, where M is the rare earth element Dy. The zirconium alloy powder contains 524 ppm C, 1085 ppm O, and 662 ppm N.

[0169] Zirconium alloy powder was added to rare earth iron-based alloy coarse powder and then fed into an air jet mill. An antioxidant was then added, and the mixture was crushed to obtain a particle size D. 50 The magnetic powder has a particle size of 3.74 μm. Based on the mass of rare earth iron-based alloy coarse powder, the amount of zirconium alloy powder used is 0.15 wt%, and the amount of antioxidant used is 0.9 wt‰.

[0170] The magnetic powder was oriented and pressed in a magnetic field to obtain a density of 3.85 g / cm³. 3 The pre-compressed billet was subjected to isostatic pressing to obtain a density of 4.30 g / cm³. 3 The blank.

[0171] The blank was sintered at 1085℃ for 5.8 hours, and then cooled to 25℃ by forced air to obtain a sintered body. The sintered body was subjected to a first-stage aging treatment at 905℃ for 1.5 hours, followed by a second-stage aging treatment at 546℃ for 4 hours. After the second-stage aging treatment, nitrogen gas at 25℃ was introduced and cooled to 25℃ to obtain a rare earth iron-based permanent magnet.

[0172] Comparative Example 3

[0173] Except for the absence of zirconium alloy powder, it is the same as in Example 3.

[0174] The performance test results of the rare earth iron-based permanent magnets obtained in Example 3 and Comparative Example 3 are shown in Table 3.

[0175] Table 3 Performance test results of rare earth iron-based permanent magnets

[0176] serial number Remanence / kGs Coercivity / kOe Maximum magnetic energy product / MGOe Example 3 14.43 15.83 51.54 Comparative Example 3 14.20 13.85 49.90

[0177] Example 4

[0178] The raw materials are vacuum smelted to obtain rare earth iron-based alloy strips; the rare earth iron-based alloy strips are then hydrogen-crushed to obtain rare earth iron-based alloy coarse powder. The particle size D of the rare earth iron-based alloy coarse powder is... 50 The particle size is 144 μm. The composition of the rare earth iron-based alloy coarse powder is: PrNd 29.8 wt%, Cu 0.15 wt%, Co 0.6 wt%, Al 0.5 wt%, Ga 0.25 wt%, Zr 0.1 wt%, B 0.90 wt%, Fe balance. The mass ratio of Pr to Nd is 25:75.

[0179] Zirconium alloy powder was obtained by processing the first zirconium-containing amorphous slag, the defective zirconium-containing amorphous casting, and the second zirconium-containing amorphous slag. The processing method was as follows: ultrasonic cleaning in anhydrous ethanol, followed by mechanical crushing to a particle size of less than 1 mm; then, petroleum ether was added for disc milling. The chemical composition of the first zirconium alloy powder formed from the zirconium-containing amorphous slag is as follows: Zr 58 Cu 30 M 12 The first zirconium alloy powder contains 424 ppm of carbon, 1242 ppm of oxygen, and 462 ppm of nitrogen. The second zirconium alloy powder, formed from a zirconium-containing amorphous substandard casting, has the following chemical composition: Zr... 50 Cu 40 M 10The composition of the zirconium alloy powder is as follows: M represents Ni, Si, and B elements, with a molar ratio of Ni, Si, and B of 60:35:5. The second zirconium alloy powder contains 324 ppm C, 1064 ppm O, and 382 ppm N. The third zirconium alloy powder formed from the second zirconium-containing amorphous slag has the following chemical composition: Zr 68 Cu 27 M5, where M represents Al and Si elements, with a molar ratio of Al to Si of 86:14. The third zirconium alloy powder contains 412 ppm C, 642 ppm O, and 362 ppm N. First, second, and third zirconium alloy powders are mixed in a mass ratio of 8:12:80 to form a particle size D. 50 It is a 6.2μm mixed zirconium alloy powder.

[0180] After adding mixed zirconium alloy powder to rare earth iron-based alloy coarse powder, the mixture is fed into an air jet mill, then an antioxidant is added, and after crushing, a particle size D is obtained. 50 The magnetic powder has a particle size of 3.65 μm. Based on the mass of rare earth iron-based alloy coarse powder, the amount of mixed zirconium alloy powder is 0.12 wt%, and the amount of antioxidant is 0.9 wt‰.

[0181] The magnetic powder was oriented and pressed in a magnetic field to obtain a density of 4.18 g / cm³. 3 The pre-pressed billet is then subjected to isostatic pressing to obtain the billet.

[0182] The blank was sintered at 1095℃ for 3.5 hours, and then cooled to 25℃ by forced air to obtain a sintered body. The sintered body was subjected to a first-stage aging treatment at 925℃ for 1 hour, followed by a second-stage aging treatment at 565℃ for 3 hours. After the second-stage aging treatment, nitrogen gas at 25℃ was introduced and cooled to 25℃ to obtain a rare earth iron-based permanent magnet.

[0183] Comparative Example 4

[0184] Except for the absence of zirconium alloy powder, it is the same as in Example 4.

[0185] The performance test results of the rare earth iron-based permanent magnets obtained in Example 4 and Comparative Example 4 are shown in Table 4.

[0186] Table 4 Performance test results of rare earth iron-based permanent magnets

[0187]

[0188]

[0189] Example 5

[0190] The raw materials are vacuum smelted to obtain rare earth iron-based alloy strips; the rare earth iron-based alloy strips are then hydrogen-crushed to obtain rare earth iron-based alloy coarse powder. The particle size D of the rare earth iron-based alloy coarse powder is... 50 The particle size is 143 μm. The composition of the rare earth iron-based alloy coarse powder is: PrNd 29.5 wt%, Cu 0.25 wt%, Co 0.55 wt%, Al 0.45 wt%, Ga 0.2 wt%, Zr 0.25 wt%, B 0.95 wt%, Fe balance. The mass ratio of Pr to Nd is 25:75.

[0191] Substandard zirconium-containing amorphous alloy castings were ultrasonically cleaned with anhydrous ethanol, mechanically crushed to a particle size of less than 1 mm, and then ground in a disc mill with petroleum ether to obtain a particle size D. 50 The zirconium alloy powder has a particle size of 6.8 μm. The chemical composition of the zirconium alloy powder is Zr. 44 Cu 40 M 16 The zirconium alloy powder contains Al, Ti, and Co elements in a molar ratio of 30:65:5. The powder contains 524 ppm of carbon, 975 ppm of oxygen, and 602 ppm of nitrogen.

[0192] Zirconium alloy powder was added to rare earth iron-based alloy coarse powder and then fed into an air jet mill. An antioxidant was then added, and the mixture was crushed to obtain a particle size D. 50 The magnetic powder has a particle size of 3.83 μm. Based on the mass of rare earth iron-based alloy coarse powder, the amount of zirconium alloy powder is 0.1 wt%, and the amount of antioxidant is 0.9 wt‰.

[0193] Magnetic powder was oriented and pressed in a magnetic field to obtain a density of 4.0 g / cm³. 3 The pre-compressed billet was subjected to isostatic pressing to obtain a density of 4.36 g / cm³. 3 The blank.

[0194] The blank was sintered at 1098℃ for 4 hours, and then cooled to 25℃ by forced air to obtain a sintered body. The sintered body was subjected to a first-stage aging treatment at 895℃ for 1 hour, followed by a second-stage aging treatment at 515℃ for 3 hours. After the second-stage aging treatment, nitrogen gas at 25℃ was introduced and cooled to 25℃ to obtain a rare earth iron-based permanent magnet.

[0195] Comparative Example 5

[0196] Except for the absence of zirconium alloy powder, it is the same as in Example 5.

[0197] The performance test results of the rare earth iron-based permanent magnets obtained in Example 5 and Comparative Example 5 are shown in Table 5.

[0198] Table 5 Performance test results of rare earth iron-based permanent magnets

[0199] serial number Remanence / kGs Coercivity / kOe Maximum magnetic energy product / MGOe Example 5 14.46 15.20 51.75 Comparative Example 5 14.30 13.67 50.68

[0200] As shown in Tables 1 to 5 above, compared with rare-earth iron-based permanent magnets without zirconium alloy powder, the magnetic properties of rare-earth iron-based permanent magnets with zirconium alloy powder prepared according to the method of the present invention are significantly better than those of the comparative example. The increase in coercivity is 2% to 15%, and the increase in maximum energy product is 1.5% to 3%. This not only solves the problem of high-value recycling of zirconium alloys, but also obtains high-performance sintered NdFeB magnets without the addition of rare-earth alloys.

[0201] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A method for preparing a rare-earth iron-based permanent magnet, characterized in that, Includes the following steps: 1) The raw materials, including rare earth iron-based alloy coarse powder and at least one zirconium alloy powder, are pulverized by an air jet mill to obtain magnetic powder; the total amount of zirconium alloy powder used is 0.05 to 0.5 wt% based on the weight of the rare earth iron-based alloy coarse powder. 2) The magnetic powder is molded to obtain a blank, and the blank is heat-treated to obtain the rare earth iron-based permanent magnet; The rare earth iron-based alloy coarse powder includes: The zirconium alloy powder has the following composition: Zr a With b M c Wherein, 25≤a≤70, 20≤b≤70, 1≤c≤20; M is selected from one or more of Hf, Ni, Co, Al, Be, Dy, Tb, Ni, Si, B, Sn and Ti; Where a, b, and c represent the molar or atomic parts of Zr, Cu, and M, respectively.

2. The preparation method according to claim 1, characterized in that, The zirconium alloy powder is selected from one or more of the following: (A) 40≤a≤50, 40≤b≤50, 5≤c≤15, M is Hf, Ni and Co; where the molar ratio of Hf, Ni and Co is (0.5~2):(1~3):(6~8); (B) 50≤a≤65, 20≤b≤40, 5≤c≤15, M is Al, Be and Co; where the molar ratio of Al, Be and Co is (7~9):(0.5~3):(0.5~3); (C) 25≤a≤40, 50≤b≤70, 1≤c≤5, M is Dy; (D) 55≤a≤65, 20≤b≤40, 8≤c≤17, M is Al, Be and Co; where the molar ratio of Al, Be and Co is (7~9):(0.5~3):(0.5~3); (E)40≤a≤55,30≤b≤48,5≤c≤15,M is Ni, Si and B;wherein, the molar ratio of Ni, Si and B is (5~7):(2~5):(0.1~1); (F) 60≤a≤70, 22≤b≤38, 5≤c≤15, M is Al and Si; where the molar ratio of Al to Si is (7.5~9.5):(0.5~2.5); (G)35≤a≤55,30≤b≤45,10≤c≤20,M is Al, Ti and Co; wherein the molar ratio of Al, Ti and Co is (1~4):(4.5~7.5):(0.1~1).

3. The preparation method according to claim 1, characterized in that, The zirconium alloy powder contains less than or equal to 1000 ppm of carbon, less than or equal to 1500 ppm of oxygen, and less than or equal to 1000 ppm of nitrogen.

4. The preparation method according to claim 1, characterized in that, The raw materials also contain one or more of antioxidants and lubricants; The antioxidant is selected from one or more of the following: triethanolamine, methyl octanoate, methyl lauryl oleate, isooctyl oleate, methyl palmitate, methyl oleate, triethanolamine oleate, and tributyl borate. Based on the mass of rare earth iron-based alloy coarse powder, the lubricant dosage is 0.2–1.8 wt‰; The lubricant is selected from amide compounds containing 10 to 40 carbon atoms.

5. The preparation method according to claim 1, characterized in that, The zirconium alloy powder is amorphous, and the sources of the zirconium alloy powder include slag, casting residue, and defective products.

6. The preparation method according to claim 1, characterized in that, The heat treatment in step 2) includes the following steps: The rare earth iron-based permanent magnet is obtained by sintering at 1050-1125℃ for 2-6 hours; the sintered body is then subjected to a first-stage aging treatment at 880-950℃ for 0.5-5 hours; and then subjected to a second-stage aging treatment at 400-630℃ for 2-5 hours.

7. A rare-earth iron-based permanent magnet, characterized in that, The rare earth iron-based permanent magnet is prepared by the preparation method described in any one of claims 1 to 6.

8. The rare earth iron-based permanent magnet according to claim 7, characterized in that, The rare-earth iron-based permanent magnet contains zirconium-containing compounds, which are distributed in at least one region as shown below in the form of laths and / or regular particles: (I) Grain boundary region; (II)Re2Fe 14 B main phase grain edges.

9. The use of a zirconium alloy in improving the magnetic properties of rare-earth iron-based permanent magnets, characterized in that, The zirconium alloy has the following composition: Zr a With b M c Wherein, 25≤a≤70, 20≤b≤70, 1≤c≤20; M is selected from one or more of Hf, Ni, Co, Al, Be, Dy, Tb, Ni, Si, B, Sn and Ti; Where a, b, and c represent the molar or atomic parts of Zr, Cu, and M, respectively; The rare earth iron-based permanent magnet includes:

10. The use according to claim 9, characterized in that, The magnetic properties are selected from one or more of coercivity, remanence, and maximum energy product.

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